Fabrication of devices such as semiconductor devices may involve deposition of various dielectric, conductive, or semiconductive films in or over raised or recessed features on a substrate. Deposition of films that are conformal to the underlying topography of a substrate can be challenging, particularly with an increase in aspect ratios and decrease in critical dimensions of features.
One example of a film that may be used in device fabrication is silicon nitride (SiN). Silicon nitride thin films have unique physical, chemical, and mechanical properties and thus are used in a variety of applications. For semiconductor devices, for example, SiN films may be used in diffusion barriers, gate insulators, sidewall spacers, encapsulation layers, strained films in transistors, and the like. Conventional methods of depositing SiN films may result in overhang when used to deposit SiN films in high aspect ratio features. As device dimensions continue to shrink, there is an increasing demand to deposit conformal SiN films and other types of films in high aspect ratio features.